Northern Australian temperature outlook

Warmer season more likely for north coasts

Text details of chance of warmer maximum and minimum temperatures

Summary

• Warmer days are more likely over much of the Top End, and Cape York Peninsula, with cooler days more likely over the southern NT and southern Queensland
• Warmer nights are more likely over the northern NT, and northern Queensland
• Climate influences include a warmer than normal eastern Indian Ocean, a neutral tropical Pacific, and warmer than average sea surface temperatures around northern Australia
• Skill for maximum temperatures is moderate over northern Australia, with minimum temperature skill moderate over most of northern Australia.

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Details

There’s a greater than 60% chance of the June to August maximum temperature exceeding the long-term median maximum temperature over the Top End and the Cape York Peninsula (see map above). Probabilities exceed 80% over far north Cape York Peninsula and the Torres Straight. Such odds mean that for every ten years with similar climate patterns to those currently observed, about six to eight years would be expected to be warmer than average over these areas, while about two to four years would be cooler.

Conversely, there is a 35 to 40% chance of warmer than normal days over the southern NT and southern Queensland. In other words, there is a 60 to 65% chance of cooler than normal days over this area.

The chance that the average minimum temperature for June to August will exceed the long-term median minimum temperature is in excess of 60% over the northern NT, and the Cape York Peninsula.

Over the rest of north-eastern Australia, the chances of warmer or cooler night-time temperatures are roughly equal.

Climate influences

The tropical Pacific has remained ENSO-neutral since mid-2012. Climate models surveyed by the Bureau of Meteorology suggest sea surface temperatures in the tropical Pacific Ocean are likely to sit on the cool side of neutral during the next few months.

Four of five international models surveyed by the Bureau favour the development of a negative Indian Ocean Dipole (IOD) event sometime later in 2013. A negative IOD during the dry season increases the chances of above normal humidity levels and rainfall (and thus cloud amount) over central and northern Australia. Increased cloudiness reduces sunshine hours, and hence daytime temperatures, as well as acting as a blanket during the night, keeping night-time temperatures higher than average.

Warmer than normal ocean surface temperatures currently surround northern Australia. These warm ocean temperatures will influence air temperatures in tropical coastal areas the most.

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Outlook confidence

Outlook confidence (or accuracy) is measured by comparing how often the outlook favoured a particular category (for instance, when above median rainfall was more likely to occur than below median rainfall in a particular season), and that the more likely category was then subsequently observed. This measurement of skill is known as "Percent Consistent", and has been tested over the period from 1981 to 2010.

Strong consistency means that tests of the model on historical data show a strong relationship between the most likely outlook category (above/below median) and the verifying observation (above/below median). In areas with strong consistency, relatively high confidence can be placed in future outlook probabilities. Very weak consistency means the historical relationship, and therefore outlook confidence, is low. In the places and seasons where the outlooks are most skilful, the category of the eventual outcome (above or below median) is consistent with the category favoured in the outlook about 75% of the time. In the least skilful areas, the outlooks perform no better than chance.

A random forecast of above median rainfall will be correct about 50% of the time. For this reason, the green shading on the map shows areas where the model has greater than 50% accuracy only. In areas which are not coloured in green on the map, some caution should be taken when using the forecast, notably at times when there is not a strong driver of our climate (e.g., no El Niño or La Niña is present; for commentary on the state of the main climate drivers, please see our ENSO Wrap Up).

The skill at predicting seasonal maximum temperature is good for most of the year, with the lowest point during the winter seasons. Of the variables predicted (i.e. rainfall, and maximum and minimum temperature), maximum temperature performs best. The skill at predicting seasonal minimum temperature peaks during summer, late autumn and late spring. Skill is lowest during late summer and late winter.

What is normal for this period?

These maps show the median (or 50th percentile) maximum and minimum temperature for the given three months. The median temperatures are calculated from the 1981-2010 period.

The maps will differ from other median maps on the Bureau's website. This is because the dynamical model forecasts use an averaging period of 1981-2010. The quality of the dynamical model forecasts is in-part determined by the coverage and accuracy of the observations fed into it. Therefore, to be consistent from one year to the next, the Bureau has only run the model during the modern satellite era.